Liquid crystal itself is non-luminous, and for a liquid crystal display (LCD) device such as a liquid crystal television, an external backlight source needs to be provided so as to display an image. Depending on its arrangement position, the backlight source includes an edge-type one and a direct-type one. The former has been widely used in small-size LCD devices due to its advantages such as fewer light-emitting elements being required, low production cost and small thickness.
For the edge-type backlight source, its light strips are arranged at a side surface of a light guide plate, and the smaller a distance between the light strip and the light guide plate, the higher a light efficiency of a light beam entering the light guide plate. Along with an increase in a size of the backlight source, more heat may be generated by the light strips, so the light guide plate may easily be expanded due to the generated heat. During the thermal expansion, when the light guide plate is pressed and deformed, the quality of the backlight source will be adversely affected. In order to provide sufficient room for the thermal expansion of the light guide plate, it is necessary to increase the distance between the light strip and the light guide plate. Hence, there is a conflict between providing sufficient room for the thermal expansion and having a high light efficiency.